Retrofit AHK Westfalia: Wiring Pins 9 & 10

Hi everyone,
I have an aftermarket tow hitch from Westfalia installed on my Audi A3 8PA, manufactured in MJ11. It is fully diagnostic-capable. Apparently, it's a re-labeled OEM control unit (the labeling on the control unit has been laser-etched).

The wiring configuration of the Westfalia connector is similar to Audi wiring diagrams, but I'm unable to get power to terminal 15 (PIN 10) for the trailer hitch or terminal 30 (PIN 9) from the control unit.
I've also tried all the encodings.
"This helped me bypass terminal 30 completely, going around the control unit (which is also how Westfalia does it with their optional wiring harness for terminal 30)."

Does anyone know why it's not possible to use an aftermarket control unit that replicates the original equipment manufacturer (OEM) functionality?

Best regards,
pretzelman01

Hi there,
It is possible that not all connections to the AHK socket are intended for use. For example, in my A4, contacts 10 and 11 are not connected by default (e.g., refrigerator, charging of the caravan battery).
Contact 9 - Long-lasting adhesive - should be available now.
hg
Herbert.

To begin with: According to my wiring diagram for the A3, there was never a provision for pin 10+11 (charging cable). Only pin 9 + 13 (constant voltage) were specified.

During retrofitting, the "Dauerplus" (permanent positive) and "Ladeplus" (charging positive) wires leading to the battery are often omitted and then sold as accessories. Therefore, first check: Is there +12V on pins 11+12 of connector T12b? And additionally, with the ignition on, is there also +12V on pins 2+9 of connector T12b?

"It should definitely be permanently active, but Volkswagen simply switched it off in some vehicle generations, either with the ignition or with a time delay. (The ability of the towing vehicle to start and avoiding entries in the breakdown statistics were more important than correct functionality)."

If all four voltages are correct, I would take a look at the control unit (STG). As far as I remember, the AHK control unit is a simple plastic housing that is just clipped in place. I would open it up and see what's connected to pin T16h (which goes to pin 9 of the module). If I recall correctly, on my Westfalia STG, it was simply jumpered with a pin from T12b. So, you only need voltage at the correct pin of T12b. The control unit itself has no influence on that.

On the other hand, if the central control unit (STG) cannot intervene anyway, then the question arises as to what advantage there would be in routing data through the STG.

guste100 wrote:

To begin with: According to my wiring diagram for the A3, there was never a pin 10+11 (charging cable) included. Only pin 9 + 13 (constant voltage) were specified.

Okay, so pin 9 is constant positive voltage, and pin 10 is switched according to the Audi wiring diagram. Ground connections are through pins 3 and 13.

Quote:

During retrofitting, the "Dauerplus" (permanent positive) and "Ladeplus" (charging positive) wires to the battery are often omitted and then sold as accessories. Therefore, first check: Is there +12V on T12b pin 11+12? And additionally, with the ignition on, is there also voltage on T12b pin 2+9?

Actually, it was missing, but I've added it according to the Audi wiring diagram. All voltages are present at the control unit (STG), but nothing is being output.

Quote:

Make sure to check the latter as well. Although it is supposed to be a continuous positive voltage, VW simply switched it off (or with a time delay) in some vehicle generations. (The ability of the towing vehicle to start and avoiding entries in the breakdown statistics were more important than correct function).

Quote:

If all four voltages are correct, I would check the control unit (STG). As far as I remember, the AHK STG is a simple plastic housing that is only clipped in place. I would open it up and see what is connected to pin T16h (which goes to pin 9 of the module). If I recall correctly, in my Westfalia STG, it was simply jumpered with a pin from T12b. So, you just need voltage at the correct pin of T12b. The STG has no way of influencing this. On the other hand: If the central control unit

cannot intervene anyway, then the question arises as to what advantage it would offer to route data through the central control unit. }

That's exactly why I connected it directly to terminal 30 now... But it's still strange. Opening the control unit again would be a good idea. The only other reason for me would be the deactivation of terminal 30 due to undervoltage.

Thank you for your input!

pretzel man

One more thing I noticed:
In the wiring diagram, there's a peculiar connection from T16h pin 14+15 that is strangely labeled. It might be worth checking if this connection exists and, if not, trying the other configuration. (I have no idea whether this actually has anything to do with the constant power supply.)

The connection is marked as "incoming" in my wiring diagram, and this small connector is plugged into the socket. Since both the wiring harness and the control unit are from Westfalia, I assume it's correct.
The plan is supposed to be valid from May 2009, and my car's registration number (MJ11) should fit that timeframe as well. Hopefully, it will work out.

Best regards,
pretzel man